/*
 * object.watch polyfill
 *
 * 2012-04-03
 *
 * By Eli Grey, http://eligrey.com
 * Public Domain.
 * NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
 */

// object.watch
if (!Object.prototype.watch) {
  Object.defineProperty(Object.prototype, "watch", {
    enumerable: false
    , configurable: true
    , writable: false
    , value: function (prop, handler) {
      var
        oldval = this[prop]
        , newval = oldval
        , getter = function () {
          return newval;
        }
        , setter = function (val) {
          oldval = newval;
          return newval = handler.call(this, prop, oldval, val);
        }
      ;

      if (delete this[prop]) { // can't watch constants
        Object.defineProperty(this, prop, {
          get: getter
          , set: setter
          , enumerable: true
          , configurable: true
        });
      }
    }
  });
}

// object.unwatch
if (!Object.prototype.unwatch) {
  Object.defineProperty(Object.prototype, "unwatch", {
    enumerable: false
    , configurable: true
    , writable: false
    , value: function (prop) {
      var val = this[prop];
      delete this[prop]; // remove accessors
      this[prop] = val;
    }
  });
}